4SY-2.9型油菜割晒机机架振动分析及改进

针对4SY-2.9型油菜割晒机因各部件运动产生的激振力随机不定而引起机架振幅大的问题,为降低割晒机工作时共振,对其机架进行建模,导入ANSYS Workbench中求解自由模态下机架的模态频率和振型,并通过模态试验与仿真分析结果对比验证有限元模型的准确性。通过分析机架外部激振频率特点和仿真结果,提出增加机架拱门结构的设计方案,开展拱门圆管厚度与安装位置仿真试验。优化后机架第1阶模态频率调整到15.339 Hz,避开了输送带弹齿和割刀激振力的激励频率范围,有效避免其共振产生。对优化后的机架模型进行有限元静力学分析,结果表明机架满足强度要求。割晒机在空载状态下,对安装机架拱门与未安装拱门纵梁最大变形点处采集加速度时域信号,并通过FFT频谱分析得到功率谱分析图,试验结果表明:测点最大峰值点X方向幅值降低了71.47%,Y方向幅值降低了70.60%,Z方向幅值降低了70.21%。田间试验表明:改进的油菜割晒机田间通过性好,作业效率高,能实现有序中间条铺,条铺宽度满足后续捡拾脱粒机作业幅宽;割晒的油菜平均铺放宽度为1 674 mm,割茬平均高度为330 mm,平均堆放高度为603 mm。优化后的油菜割晒机机架动态性能良好,作业质量满足后续工序作业要求。该研究可为同类宽幅机架的设计研究提供参考。

Vibration analysis and improvement for frame of 4SY-2.9 typed rape windrower

Abstract: In China, the rape harvesting mechanization level is low and traditional manual harvesting is so poor, so it is necessary to develop rape windrower to improve productivity and reduce cost. The pros and cons of the frame design play an important role on the comfort and working reliability of the windrower machine manipulation. The frame of 4SY-2.9 rape windrower is the base and bears the load of whole assembly, and during the rape windrower working, the exciting vibrations from cutter and the conveyor belt spring tooth will cause the rape windrower to vibrate. Because those excitation frequencies were closed to or overlapped the natural frequencies of the rape windrower, the frame of 4SY-2.9 rape windrower will produce resonance seriously. To improve the quality of laying, reducing the vibration amplitude of the frame of rape windrower is a feasible way, and the finite element method will solve this problem by using structural modal analysis to get the dynamic characteristics of the frame structure. In order to solve the problem of the large amplitude of the rack caused by the random exciting force produced by the movement of various parts of the machine, in this paper, we modeled the rack and imported the model in ANSYS Workbench to work out the frequency and vibration mode of the rack under the free modal, and we verified the accuracy of the finite element model through the contrast of the modal test and the simulation analysis results. It was found that the relative error between the 2 results was in a reasonable range, so the rationality of frame modal analysis was verified. Based on the analysis of the characteristics of the external excitation frequency of the frame and the simulation results, the design scheme was put forward, which was increasing the frame arch structure, and the simulation experiment on the pipe thickness and installation position of arch was carried out. The optimized rack''s first-order modal frequency was adjusted to 15.339 Hz, so that it avoided the excitation frequency of the conveyor belt spring tooth and the cutter effectively which could cause the frame resonance. Through the finite element statistics analysis on the optimized model of the frame, the result showed that the strength of the frame met the requirements. Windrower on no-load condition collected acceleration time-domain signal of the biggest deformation point of longitudinal beam, and obtained the fast fourier transform power spectral analysis diagram under the condition with and without the installation of the arch. The test results showed that the amplitude along X direction at the largest peak point of test point decreased by 71.47%, the amplitude along Y direction was reduced by 70.60%, and the amplitude along Z direction was reduced by 70.21%. Field experiments showed that 4SY-2.9 rape windrower had a good operation performance with a good throughput capacity and a high work efficiency, and achieved an orderly intermediate strip paving. The paving width met the requirement of the working width of the collecting sheller. After cut down and dried, the average paving width of rapeseed stalks was 1 674 mm, the average stubble height of rapeseed stalks was 330 mm, and the average stack height of rapeseed stalks was 603 mm. The optimized rape windrower frame had a good dynamic performance, and the field operation effect could meet the requirement of the actual production. This research may provide references for the design and improvement of the similar broad frames.